linux-kernel - Re: [PATCH] x86: kvm: avoid unused variable warning

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Date:   Wed, 22 Aug 2018 13:51:47 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>, Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org
Cc:     "H. Peter Anvin" <hpa@...or.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Liran Alon <liran.alon@...cle.com>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: kvm: avoid unused variable warning

On 20.08.2018 23:37, Arnd Bergmann wrote:
> Removing one of the two accesses of the maxphyaddr variable led to
> a harmless warning:
> 
> arch/x86/kvm/x86.c: In function 'kvm_set_mmio_spte_mask':
> arch/x86/kvm/x86.c:6563:6: error: unused variable 'maxphyaddr' [-Werror=unused-variable]
> 
> Removing the #ifdef seems to be the nicest workaround, as it
> makes the code look cleaner than adding another #ifdef.
> 
> Fixes: 28a1f3ac1d0c ("kvm: x86: Set highest physical address bits in non-present/reserved SPTEs")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  arch/x86/kvm/x86.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 4a74a7cf0a8b..506bd2b4b8bb 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6576,14 +6576,12 @@ static void kvm_set_mmio_spte_mask(void)
>  	/* Set the present bit. */
>  	mask |= 1ull;
>  
> -#ifdef CONFIG_X86_64
>  	/*
>  	 * If reserved bit is not supported, clear the present bit to disable
>  	 * mmio page fault.
>  	 */
> -	if (maxphyaddr == 52)
> +	if (IS_ENABLED(CONFIG_X86_64) && maxphyaddr == 52)
>  		mask &= ~1ull;
> -#endif
>  
>  	kvm_mmu_set_mmio_spte_mask(mask, mask);
>  }
> 

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 

Thanks,

David / dhildenb